The present invention relates to a thrust reverser for a turbofan-type turbojet engine in which pivotable thrust reverser doors change the direction of the turbofan air to provide thrust reversing forces.
Turbofan-type turbojet engines are well known in the art and typically comprise an annular housing concentrically surrounding the turbojet engine housing to define an annular, cold flow air duct extending along the longitudinal axis of the engine. A fan, driven by the turbojet engine, is typically located in the upstream portion of this duct and forces air through the duct to augment the thrust of the turbojet engine.
In such engines having a relatively high bypass ratio, a thrust reversing device may be associated with the annular housing to redirect the air passing through the cold flow air duct to provide the thrust reversing forces. It is known to provide one or more pivotable doors in the annular housing to redirect the air when necessary.
Such a typical installation is illustrated in FIG. 1 wherein the annular housing has an upstream portion 1 formed by an outer panel 4 and an inner panel 5 joined by frame structure 6. The thrust reverser 2, comprising a pivotable door 7, extends between portion 1 and a downstream portion 3 to normally cover a laterally facing opening when the turbofan engine operates in the forward thrust mode. In this mode, outer door panel 9 is substantially flush with the outer panel 4 and the exterior surface of downstream cone 3 to provide a smooth airflow 10 over the exterior of the annular housing.
Frame structure 6 supports actuating cylinder 7a which has its extendible and retractable piston rod attached to internal structure 12 of the thrust reverser door 7. Structure 12 interconnects outer door panel 9 with inner door panel 11. These panels are also interconnected at their upstream edges by baffle member 13. In known fashion, extension of the piston rod of actuator 7a causes the door 7 to pivot such that its upstream end portion extends outwardly and a downstream end portion extends inwardly to block off the airflow 15 flowing through the cold flow air duct. The door redirects the air outwardly through the side of the annular housing to provide a thrust reversing force.
A deflection edge 8 extends from the inner housing panel 5 to minimize the turbulence of the air passing through the opening in the thrust reversing mode. In order to accommodate this deflection edge 8 when the door 7 is in its closed, forward thrust position, the inner door panel 11 is oriented such that its upstream end is closer to the outer panel 9 than is its downstream end. This orientation of the inner door panel, while being effective in the open, thrust reversing position of the door, defines an internal cavity 16 bounded by the inner door panel 11, upstream baffle 13, deflection edge 8 and the theoretical airflow line 14 extending between the inner housing panel 5 and the downstream cone 3. Line 14 represents the ideal, theoretical airflow through the airflow duct between inner housing panel 5 and downstream cone 3. The cavity 16 causes disturbances and perturbations in the air flow 15 passing through the cold flow air duct, thereby reducing its efficiency in the forward thrust mode.
Examples of such typical prior art thrust reversing door systems can be found in French patent Nos. 2,559,838; 2,506,843; 2,486,153; and 2,030,034. None of the systems illustrated in these patents, however, have resolved the problem of maintaining a smooth airflow path through the cold-flow air duct in the forward thrust mode as well as maximizing the efficiency of the door in the reverse thrust mode.
U.S. Pat. No. 3,605,411 discloses a thrust reversing door associated with an annular fan housing in which the position of the inner door panel relative to the outer door panel varies between the forward thrust mode and the reverse thrust mode. However, the means to actuate and drive the door between its open and closed positions, utilizing a slider and a guide roller, have not proven entirely satisfactory.